An electrochemical oxygen sensor with two working electrodes called a measuring electrode and a protective electrode, a counterelectrode called an auxiliary electrode, as well as a reference electrode is described in DE 197 26 453 C2. The measuring electrode, the protective electrode and the auxiliary electrode are arranged plane-parallel to one another with mats introduced between them, which are impregnated with an electrolyte and act as separators. The sensitivity of the sensor to vibration is considerably reduced by this type of arrangement. The electrolyte with the electrodes located in it is screened from the gas to be measured via a diffusion membrane consisting of polytetrafluoroethylene. All electrodes used are made of the same material, e.g., gold, platinum or alloys thereof
An electrochemical gas sensor with a diffusion membrane consisting of a polymer containing bis-2,2-trifluoromethyl-4,5-difluoro-1,3-dioxol, especially a copolymer from the monomers bis-2,2-trifluoromethyl-4,5-difluoro-1,3-dioxol and tetrafluoroethylene (trademark “Teflon® AF”) has been known from DE 200 22 508 U1. Shorter response time and improved sensitivity to gases such as oxygen and hydrogen can be observed during the measurement with such diffusion membranes.